A robust low-delay CELP speech coder at 16 kbits/s

Abstract

A candidate algorithm for the new CCITT 16-kb/s speech coding standard is presented. This algorithm is based on backward-adaptive CELP (code-excited linear prediction) where the predictor and the excitation gain are updated by analyzing previously quantized signals. The only information transmitted is the excitation vector with a size as small as five samples so as to achieve a one-way coding delay of less than 2 ms. With a clear channel, this 16-kb/s coder slightly outperformed the CCITT standard 32 kb/s ADPCM (adaptive differential pulse code modulation) (G.721) in speech quality as measured by the mean opinion score (MOS). With noisy channels, the coder scored slightly higher than G.721 fora bit-error rate of 10/sup -2/ and significantly higher (by a margin of 0.5) for bit-error rate of 10/sup -3/.<>